Method of manufacturing tape wiring substrate

ABSTRACT

A method of manufacturing a tape wiring substrate, by which the production cost can be reduced by a simplified manufacturing process. A fine wiring pattern having fine pitches can be formed. The method of manufacturing a tape wiring substrate includes preparing a base film, forming a metal layer on the base film, and processing the metal layer into a wiring pattern using a laser. In addition, the metal layer is partially removed using the laser, and a wiring pattern is formed by a subsequent wet etching.

This application claims priority from Korean Patent Application No. 10-2004-0017943 filed on Mar. 17, 2004 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method of manufacturing a tape wiring substrate, and more particularly, to a method of manufacturing a tape wiring substrate, by which a wiring pattern is formed using a laser.

2. Description of the Related Art

According to a recent trend for thin, compact, highly integrated, high speed and multi-pin semiconductor devices, tape wiring substrates have been increasingly employed in techniques of mounting semiconductor chips. The tape wiring substrates are configured so that a wiring pattern layer is formed on a base film made of an insulating material such as polyimide resin. It is possible to apply a tape automated bonding (TAB) technique for bonding leads connected to the wiring pattern layer to bumps previously formed on a semiconductor chip at one time in the tape wiring substrates. The tape wiring substrates are referred to as a TAB tape owing to such a characteristic.

FIGS. 1A through 1D are cross-sectional views successively showing a method of manufacturing a tape wiring substrate according to a prior art.

As shown in FIG. 1A, a copper foil 120 is formed on a base film 110 made of an insulating material such as polyimide resin, using a laminating method or an electrolytic plating method.

As shown in FIG. 1B, photoresist 130 (hereinafter referred to as “PR”) is coated on the copper foil 120. Subsequently, an exposing step is performed using a light source 132 having a wavelength of several hundreds of micrometers.

As shown in FIG. 1C, the PR 130, after completing the exposing step, is developed so that the PR 130 is patterned.

As shown in FIG. 1D, the copper foil 120 is etched by patterned PR 135 using an etching mask. At this time, a wet etching step is used to etch the copper foil 120. A wiring pattern 125 is formed by removing the remaining PR 135.

As described above, in the process of manufacturing the conventional tape wiring substrate, after manufacturing the base film 110, the copper foil 120 is formed thereon and processed into the wiring pattern 125 using photolithographic etching. The photolithographic etching includes a variety of steps, including a PR coating step, an exposing step, a PR developing step, a step of etching the copper foil, and so on.

So many processing steps give rise to an increase in the volume of a production line, and volumes of materials that are consumed regularly, for example, PR, PR developer, copper foil etchant or the like, become increased, thereby inevitably increasing the production cost.

Further, since the light source 132 having a relatively large wavelength of several hundreds of micrometers is used in the conventional photolithographic etching, it is quite difficult to form a micro scale wiring pattern having fine pitches on the copper foil 120.

SUMMARY OF THE INVENTION

To solve the above-described problems, embodiments of the present invention provide a method of manufacturing a tape wiring substrate, by which production cost can be reduced by a simplified manufacturing process and a fine wiring pattern having fine pitches can be formed.

The above stated embodiments as well as other embodiments of the present invention will become readily apparent to one skilled in the art from the following description.

In accordance with an embodiment of the present invention, there is provided a method of manufacturing a tape wiring substrate comprising preparing a base film, forming a metal layer on the base film, and processing the metal layer into a wiring pattern using laser.

In accordance with another embodiemnt of the present invention, there is provided a method of manufacturing a tape wiring substrate comprising preparing a base film, forming a metal layer on the base film, partially removing an area other than a wiring pattern in the metal layer using laser, and etching the remaining area other than the wiring pattern and forming the wiring pattern.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other features and advantages of the present invention will become more apparent by describing in detail preferred embodiments thereof with reference to the attached drawings:

FIGS. 1A through 1D are cross-sectional views successively showing a method of manufacturing a conventional tape wiring substrate.

FIG. 2 is a flow chart showing a process of manufacturing a tape wiring substrate according to an embodiment of the present invention.

FIGS. 3A through 3C are cross-sectional views successively showing the process of manufacturing the tape wiring substrate of FIG. 2.

FIG. 4 is a schematic view of a structure of an exposing apparatus used in an embodiment of the present invention.

FIG. 5 is a flow chart showing a process of manufacturing a tape wiring substrate according to another embodiment of the present invention.

FIGS. 6A through 6D are cross-sectional views successively showing the process of manufacturing the tape wiring substrate of FIG. 5.

DETAILED DESCRIPTION OF THE INVENTION

Advantages and features of the present invention and methods of accomplishing the same may be understood more readily by reference to the following detailed description of preferred embodiments and the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete and will fully convey the concept of the invention to those skilled in the art, and the present invention will only be defined by the appended claims. Like reference numerals refer to like elements throughout the specification.

A flexible printed circuit board (FPC), such as a tape carrier package (TCP) or a chip on film (COF), in which a wiring pattern is formed on a base film, can be used as a tape wiring substrate in an embodiment of the present invention. The tape wiring substrate used in an embodiment of the present invention has a structure in which wiring patterns and inner leads connected thereto are formed on a thin film made of an insulating material such as polyimide resin. The tape wiring substrate used in the embodiment of present invention includes a wiring substrate applying a tape automated bonding (TAB) technique in which bumps previously formed on a semiconductor chip and the inner leads of the tape wiring substrate are bonded at one time. The above-stated tape wiring substrates are provided for illustration only.

Hereinafter, an embodiment of the present invention is explained with reference to FIGS. 2 through 4.

FIG. 2 is a flow chart showing a process of manufacturing a tape wiring substrate according to an embodiment of the present invention, FIGS. 3A through 3C are cross-sectional views successively showing the process of manufacturing the tape wiring substrate of FIG. 2, and FIG. 4 is a schematic view of a structure of an exposing apparatus used in this embodiment of the present invention.

As shown in FIG. 2, a base film is first prepared in step S210. Referring to FIG. 3A, the base film 310 is made of an insulating material having a thickness of 20-100 μm. An insulating material such as polyimide resin or polyester resin can be used as a main material of the insulating base film 310. A polyimide thin film among the base film 310 can be obtained by removing a solvent from a film obtained by coating a precursor, that is, a polyamic acid (PAA) solution in a fixed container, and then performing a curing step (not shown).

Referring back to FIG. 2, a metal layer is formed on the base film 310 in step S220. Referring to FIG. 3A, a metal layer 320 formed on the base film 310 has a thickness of about 5-20 μm and is made of a metal material, generally copper.

A method of forming a copper foil as an exemplary layer of the metal layer 320 on the base film 310 includes casting, laminating, electroplating, and so on. In the casting, the base film 310 being in a liquid form is cast on a rolled copper foil, followed by curing. In the laminating, a rolled copper foil is placed on the base film 310 and then thermally compressed. In the electroplating, a seed layer (not shown) is deposited on the base film 310, and immersed in an electrolyte having copper melted therein, followed by applying electricity thereto, thereby forming a copper foil. Here, the seed layer can be formed on the base film 310 by sputtering. The seed layer is preferably made of a material selected from the group consisting of Cr, Ti, Ni, and a combination thereof.

As shown in FIG. 2, a wiring pattern is formed using a laser in step 230. Referring to FIGS. 3A and 3B, the metal layer 320 formed on the base film 310 is etched selectively using a laser 330, forming a wiring pattern 325 to construct a predetermined circuit.

As shown in FIG. 2, solder resist 340 is coated in step 240. Referring to FIG. 3C, the solder resist 340 is coated on a portion of the base film 310 other than a predetermined portion in the wiring pattern 325 electrically connected to an external terminal to protect the wiring pattern 325 from an external impact. The solder resist 340 can be coated by a screen printing method.

Preferably, plating of Sn, Au, Ni or solder is performed on a surface of the wiring pattern 325 for the purpose of improving electric characteristics of the wiring pattern 325. Such a method in which plating is performed after coating the solder resist 340 on the wiring pattern 325 is referred to as a post-plating method. Of course, a pre-plating method in which the solder resist 340 is coated after plating on the wiring pattern 325 can be adopted in another embodiment of the present invention.

Hereinafter, a method of forming the wiring substrate using the laser will be described in detail with reference to FIG. 4.

Referring to FIG. 4, a laser exposing apparatus 400 of the present invention includes a light source 410, a fly's eye lens 420 comprised of lens arrays, an aperture 430 having a predetermined shape, a condenser lens 440 and a projection lens 460.

Here, a laser having a wavelength of 550 nm or less can be generated from the light source 410 so as to embody the wiring pattern 325 having fine pitches. Thus, a source gas of any one selected from the group consisting of ArF, KrF, XeC₁, F₂, Nd-YAG (neodymium-yttrium aluminum garnet), and CO₂ can be used as the light source 410. Further, a laser such as a laser diode can be used.

As shown in FIG. 4, the fly's eye lens 420, in which small lenses may have a hexagonal shape, like a fly's eye, or other various shapes, is disposed along a path of the laser radiation emitted from the light source 410. A beam homogenizer, e.g., the fly's eye lens 420, allows the laser radiation to be uniform in intensity and distribution when irradiating a mask 450.

Further, as the wiring pattern becomes smaller and smaller, the aperture 430 can be disposed in a path of the laser to increase the resolution of laser radiation pattern. The aperture 430 can be shaped of a dipole, quadrupole, annulus, and so on.

Thus, the laser radiation generated in the light source 410 may be converted into a substantially parallel beam by the fly's eye lens 420 and partially confined by the aperture 430.

The laser radiation passing through the aperture 430 may be irradiated onto the mask 450 through the condenser lens 440. The condenser lens 440 concentrates the laser radiation generated in the light source 410 in a desirable direction. The condenser lens 440 is not directly concerned in forming an image, but increases the uniformity of the laser when the laser is irradiated onto the mask 450.

The laser radiation having reached the mask 450 is diffracted and passes through the projection lens 460 to expose the metal layer 320 formed on the base film 310. Generally, the projection lens 460 transmits laser radiation from the mask 450 to micro-project the image of the mask pattern onto the metal layer 320. A stage 470 supports the base film 310 where the metal layer 320 is formed.

Examples of useful methods of irradiating the laser radiation emitted from the light source 410 onto the metal layer 320 formed on the base film 310 include a step-and-repeat method in which the metal layer 320 is irradiated using a stepper while the mask 450 and the stage 470 stop moving, and a step-and-scan method in which exposure is performed using a scanner while moving the mask 450 and the stage 470 in opposite directions at different moving speeds.

To accurately etch only the metal layer 320 except the wiring pattern 325, which is required to process the metal layer 320 as the wiring pattern 325, and to minimize the base film 310 located under the metal layer 320 from being damaged due to thermal energy generated from the laser, a pulse type layer is preferably used.

A preferred method of emitting laser radiation will now be described by way of example of an ArF excimer laser (wavelength of 193 nm) having a pulse energy of 200 mJ. Here, a method of emitting the laser radiation can vary according to equipment used and processing conditions. It has been shown and described that copper may be used as the metal layer 320 and polyimide may be used as the base film 310, but embodiments of the present invention are not limited to the particular embodiment described below.

In the ArF excimer laser according to an embodiment of the present invention, assuming that an etching rate with respect to copper is about 160 mJ/μm and an etching rate with respect to polyimide is about 16 mJ/μm, a process of the etching metal layer 320 having a thickness of 8 μm into the wiring pattern 325 will now be described.

To etch the metal layer 320 having the thickness of 8 μm, energy of 1280 mJ (=160 mJ/μm×8 μm) is required. Since pulse energy of the ArF excimer laser is 200 mJ, 6.4 pulses (=1280 mJ/200 mJ) is required to etch the metal layer 320 having the thickness of 8 μm. Thus, if the ArF excimer laser of 7 pulse is irradiated onto the metal layer 320, the metal layer 320 other than a portion where the wiring pattern 325 is formed is completely etched, and energy of 120 mJ (=200 μm×0.6) corresponding to 0.6 pulse is irradiated onto the base film 310. Thus, the base film 310 is further etched to a thickness of about 7.5 μm (=120 mJ/16 mJ/μm), which is, however, a negligible etching amount, that is, physical properties of the base film 310 are not adversely affected at all.

When the metal layer 320 is etched using the pulse type laser, the pulse energy of the laser can adjustably change the frequency (usually in a range of 50-300 Hz) and print “energy” (usually in a range of 5-100 W). Thus, in case pulse energy of the laser is properly adjusted, appropriately adjusting the pulse energy can reduce an etching amount of the base film 310 located under the metal layer 320, e.g., polyimide, to a minimum, but not limited to values particularly defined in the above-described embodiment. Rather, the metal layer 320 is etched while minimizing the etching amount of the base film 310 by adjusting the frequency and print energy of the laser according to a material and a thickness of the metal layer 320.

In addition, during forming of the wiring pattern 325 using the laser, the thermal energy may be transferred to not only a contact portion between the metal layer 320 and the laser 330 but also the metal layer 320 or the base film 310 adjacent to the contact portion. The thermal energy may etch the metal layer 320 around the contact portion or may deform the base film 310 under the contact portion. Thus, a refrigerant is preferably supplied to a portion where the metal layer 320 and the laser 330 contact while forming the wiring pattern 325 using laser, thereby preventing the thermal energy from being transferred to the vicinity of the contact portion. As the refrigerant, methylether, ethyl chloride, methyl formate, isobutane, dichloroethylene, methylene chloride, ethylether, ammonia, carbon dioxide, sulfur dioxide, methyl chloride and CFC-based refrigerant (Freon), etc. can be used.

Another embodiment of the present invention will now be described with reference to FIGS. 5 through 6D.

FIG. 5 is a flow chart showing a process of manufacturing a tape wiring substrate according to this embodiment of the present invention, and FIGS. 6A through 6D are cross-sectional views successively showing the process of manufacturing the tape wiring substrate of FIG. 5. To facilitate understanding, the same functional elements as those shown in the drawings of FIGS. 3A-3C which correspond to the previously described embodiment of the present invention are denoted by the same reference numerals, and a detailed explanation thereof will not be given.

As shown in FIGS. 5 and 6A, first, a base film 310 is prepared in step S510. Sequentially, a metal layer 320 is formed on the base film 310 in step S520. Here, the metal layer 320 is the same as that used in the previously described embodiment of the present invention.

Referring to FIGS. 5, 6A and 6B, the metal layer 320 formed on the base film 310 is selectively etched using the laser 330 to form a wiring pattern 625 constructing a predetermined circuit in step S530. Here, the metal layer 320 consists of a wiring pattern 625 for transmitting an electric signal and an area 622 other than the wiring pattern 625, the area 622 being necessarily removed in a subsequent step to complete the wiring pattern 625.

As shown in FIG. 6B, the area 622 other than the wiring pattern 625 is partially removed using the laser 330 to be left to a predetermined thickness. In the case of using an 8 μm thick copper foil as the metal layer 320 in a preferred embodiment of the present invention, the copper foil may be etched away to a thickness of about 7.5 μm using the laser 330 and remains to a thickness of about 0.5 μm, but the present invention is not particularly limited thereto. Rather, the thickness of the area 622 left over after laser etching can vary according to processing conditions or convenience.

As shown in FIG. 6C, the area 622 other than the wiring pattern 625 is removed by wet etching in step S540. The base film 310 disposed under the area 622 is exposed from the metal layer 320 by the wet etching. As described above, the wet etching may be preferably used to remove the wiring pattern except area 625, but the present invention is not limited thereto. For example, the area 622 other than the wiring pattern 625 can be removed by dry etching using plasma.

Preferably, in the case of using a copper foil as the metal layer 320, wet etching can be performed using an aqueous solution containing FeCl₃, FeCl, and HCl as an etchant. Alternatively, the wet etching can be performed using an aqueous solution containing CuCl₂, CuCl, and HCl as an etchant.

As shown in FIG. 6D, in order to protect the wiring pattern 625 from an external impact, a solder resist 340 or other protective material is coated on the wiring pattern 625 formed on the base film 310, exclusive of a predetermined portion electrically connected to an external terminal, in step S550.

Another preferred method involving laser etching will now be described by way of example of an ArF excimer laser (wavelength of 193 nm) having a pulse energy of 200 mJ. Here, the method using the laser can vary according to equipment used and processing conditions. It has been shown and described that copper is used as the metal layer 320 and polyimide is used as the base film 310, but the present invention is not limited to the particular embodiments described above or below.

In the ArF excimer laser according to another embodiment of the present invention, assuming that an etching rate with respect to copper is about 160 mJ/μm and an etching rate with respect to polyimide is about 16 mJ/μm, a process of etching the metal layer 320 having a thickness of 8 μm into the wiring pattern 625 will now be described.

To etch the metal layer 320 having the thickness of 8 μm, energy of 1280 mJ (=160 mJ/μm×8 μm) is required. Since pulse energy of the ArF excimer laser is 200 mJ, 6.4 pulses (=1280 mJ/200 mJ) is required to etch the metal layer 320 having the thickness of 8 μm. Thus, if the ArF excimer laser of 6 pulses is irradiated onto the metal layer 320, the metal layer 320 other than a portion where the wiring pattern 625 is formed is etched. Thus, the area 622 other than the wiring pattern 625 remains to a thickness of about 0.5 μm, which can be removed by either wet etching or dry etching using plasma.

As described above, the wiring pattern 625 can be formed using the laser 330 without causing damages to the base film 310 by simultaneously performing primarily etching using laser and secondary etching (either wet etching or dry etching).

As described above, according to the illustrative embodiments of the invention, a metal layer can be directly processed into a wiring pattern without using photoresist, unlike in the prior art. Thus, the number of processing steps is reduced and thus the production cost of the tape wiring substrate can be reduced, compared to the prior art.

In concluding the detailed description, those skilled in the art will appreciate that many variations and modifications can be made to the preferred embodiments without substantially departing from the principles of the present invention. Therefore, the disclosed preferred embodiments of the invention are used in a generic and descriptive sense only and not for purposes of limitation.

As described above, according to the method of manufacturing the tape wiring substrate of the present invention, the production cost can be reduced through a simplified manufacturing process and a fine wiring pattern having fine pitches can be formed. 

1. A method of manufacturing a tape wiring substrate comprising: preparing a base film; forming a metal layer on the base film; and etching the metal layer into a wiring pattern using a laser that produces laser radiation that is incident on the metal layer.
 2. The method of claim 1, wherein the laser generates from a source gas of any one selected from the group consisting of ArF, KrF, XeC1, F₂, Nd-YAG (neodymium-yttrium aluminum garnet), and CO₂.
 3. The method of claim 1, wherein the laser is a pulse type.
 4. The method of claim 1, wherein the laser radiation passes through a beam homogenizer before being incident on the metal layer.
 5. The method of claim 1, wherein a refrigerant is provided for the metal layer while etching the wiring pattern.
 6. The method of claim 5, wherein the refrigerant is any one selected from the group consisting of methylether, ethyl chloride, methyl formate, isobutane, dichloroethylene, methylene chloride, ethylether, ammonia, carbon dioxide, sulfur dioxide, methyl chloride, and CFC-based refrigerant (Freon).
 7. The method of claim 1, wherein the metal layer includes copper.
 8. A method of manufacturing a tape wiring substrate comprising: preparing a base film; forming a metal layer on the base film; at least partially removing an area other than a wiring pattern in the metal layer using a laser that produces radiation that is incident on the metal layer; and etching the remaining area other than the wiring pattern to form the wiring pattern.
 9. The method of claim 8, wherein the laser generates from a source gas of any one selected from the group consisting of ArF, KrF, XeC1, F₂, Nd-YAG (neodymium-yttrium aluminum garnet), and CO₂.
 10. The method of claim 8, wherein the laser is a pulse type.
 11. The method of claim 8, wherein the laser radiation passes through a beam homogenizer before being incident on the metal layer.
 12. The method of claim 8, wherein a refrigerant is provided for the metal layer while at least partially removing the area.
 13. The method of claim 12, wherein the refrigerant is any one selected from the group consisting of methylether, ethyl chloride, methyl formate, isobutane, dichloroethylene, methylene chloride, ethylether, ammonia, carbon dioxide, sulfur dioxide, methyl chloride, and CFC-based refrigerant (Freon).
 14. The method of claim 8, wherein the etching is wet etching.
 15. The method of claim 14, wherein the wet etching exposes the base film disposed under the area other than the wiring pattern.
 16. The method of claim 8, wherein the metal layer includes copper.
 17. The method of claim 15, wherein the wet etching is performed using an aqueous solution containing FeCl₃, FeCl, and HCl as an etchant.
 18. The method of claim 15, wherein the wet etching is performed using an aqueous solution containing CuCl₂, CuCl, and HCl as an etchant.
 19. The method of claim 8, wherein the forming the metal layer is performed by laminating.
 20. The method of claim 8, wherein the forming the metal layer is performed by electroplating.
 21. The method of claim 8, prior to the forming the metal layer, comprising forming a seed layer on the base film by sputtering.
 22. The method of claim 21, wherein the seed layer is made of a material selected from the group consisting of Cr, Ti, Ni, and a combination thereof. 